THE  UNIVERSITY 

OF  ILLINOIS 

LIBRARY 

630.7 
II6b 


oop-Z 


A6RICULTURAI 
U1BABY 


ING 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  No.  227 


SULFUR  IN  RELATION  TO  SOIL  FERTILITY 

BY  ROBERT  STEWART 


URBANA,  ILLINOIS,  JUNE,  1920 


CONTENTS  OF  BULLETIN  No.  227 

PAGE 

INTRODUCTION 99 

SULFUR  EEQUIREMENT  OP  PLANTS 100 

SULFUR  CONTENT  OF  THE  SOIL 100 

EFFECT  OF  SULFUR  ON  THE  PRODUCTION  OF  CROPC 101 

Loss  OF  SULFUR  IN  DRAINAGE  WATER 104 

SULFUR  CONTENT  OF  RAINFALL 106 

CONCLUSIONS..  .  108 


SULFUR  IN  RELATION  TO  SOIL  FERTILITY 

BY  EGBERT  STEWAET,  CHIEF  IN  SOIL  FERTILITY 

INTRODUCTION 

Sulfur  is  one  of  the  ten  essential  elements  of  plant  food.  It  is 
necessary  for  the  formation  of  certain  essential  oils  and  for  many 
plant  proteins  in  which  it  is  a  component  part.  These  facts  have 
been  known  for  a  long  time.  Iron,  likewise,  is  an  essential  element 
of  plant  food,  but  there  are  only  one  or  two  instances  of  its  having 
been  added  to  the  soil  with  any  economic  results.1  It  has  been 
generally  assumed  by  soil  investigators  that  the  demands  of  the  plant 
for  iron  are  so  small  and  the  supply  in  the  soil  so  large  that  it 
will  never  be  necessary  to  add  it  to  the  soil. 

With  sulfur,  also,  it  has  been  generally  assumed,  until  quite  re- 
cently, that  the  supply  in  the  soil  was  sufficient  to  meet  the  small 
requirements  of  plants  for  indefinite  periods  of  time.  The  question 
of  its  value  as  a  fertilizer  has  arisen  again  within  the  past  few  years, 
however,  as  a  result  of  several  circumstances,  one  being  the  attempt 
on  the  part  of  those  having  sulfur  materials  for  sale  to  enlarge  the 
agricultural  market  for  their  goods.  This  bulletin  brings  together 
in  summarized  form  the  available  data  on  the  subject,  and  is  pub- 
lished in  an  attempt  to  answer  the  many  questions  which  are  coming 
to  the  Experiment  Station  with  regard  to  the  use  of  sulfur  in  this  way. 

It  is  true  that  compounds  of  sulfur,  and  even  sulfur  itself,  have 
been  used  on  soils  for  long  periods  of  time.  Benjamin  Franklin  in 
this  country  was  an  early,  ardent  advocate  of  the  use  of  land-plaster, 
or  gypsum,  the  native  sulfate  of  calcium.  From  his  day  until  the 
present  the  question  of  the  use  of  land-plaster,  or  gypsum,  has  per- 
iodically arisen.  A  quarter  of  a  century  ago  this  question  occupied 
the  minds  of  soil  men  quite  prominently.  This  manifests  itself  in 
the  field  plans  of  the  Pennsylvania  and  Ohio  experiment  stations, 
where  provisions  were  made  to  test  out  the  effect  of  gypsum  on  the 
production  of  crops.  The  results  obtained  by  these  experiment  sta- 
tions are  considered  on  pages  101  to  103.  They  offer  the  best  evidence 
the  world  affords  today  of  the  lack  of  value  of  gypsum  in  crop  pro- 
duction under  actual  field  conditions,  in  humid  regions. 


1Cases  have  been  reported  from  Australia  and  Hawaii  where  iron  has  been 
used  successfully  on  special  soils  and  for  special  crops  with  favorable  results. 

99 


100 


BULLETIN  No.  227 


[June, 


SULFUR  REQUIREMENT  OF  PLANTS 

Until  1911  it  had  been  the  custom  of  analytic  chemists,  in  analyz- 
ing plants  for  sulfur,  to  burn  the  plants  and  determine  the  sulfur 
content  of  the  ash,  in  that  way  determining  their  sulfur  requirements. 
In  1911  Hart  and  Peterson  of  Wisconsin  called  attention  to  the  fact 
that  under  these  conditions  a  large  part  of  the  sulfur  escaped  in 
the  gases  and  the  reported  sulfur  content  of  vegetation  was  there- 
fore too  low.  They  redetermincd  the  sulfur  content  of  various  crops 
by  the  improved  Osborne  method,  which  consists  of  careful  fusion 
of  the  plant  material  with  sodium  peroxid,  and  found  that  the  plant 
requirements  for  sulfur  were  much  higher  than  had  been  generally 
assumed.  The  differences  so  found  may  be  readily  seen  by  a  consid- 
eration of  the  data  below. 

TABLE  1. — SULFUR  CONTENT  OF  SOME  COMMON  FARM  CROPS 


Crop 

Large 
crop 
yields 

Sulfur  in  plant 
(After  Hart  and 
Peterson) 

Sulfur  in  Ash 
(After  Wolff) 

Alfalfa  hay  

per  acre 
8  tons 
4  tons 

100  bu. 
3  tons 

100  bu. 
2^i  tons 

3  tons 

50  bu. 

2>6  tons 

perct. 
.287 
.164 

.170 
.126 

.189 
.195 

.190 

.170 
.119 

Ibs. 
45.92 
13.12 

9.52 
7.56 

6.05 
9.75 

11.40 

5.10 
5.95 

perct. 
.170 
.083 

.004 
.113 

.002 
.092 

.078 

.003 
.053 

/6s. 
27.20 
7.12 

.22 
6.78 

.06 
4.60 

4.68 

.09 
2.65 

Red  clover  

Corn,  white  

Corn  stover  

Oats  

Oat  straw  , 

Timothy  

Wheat  .-  

Wheat  straw  

These  results  were  significant.  It  was  found  that  a  hundred- 
bushel  crop  of  corn,  for  example,  instead  of  removing  only  a  fraction 
of  a  pound  of  sulfur,  actually  removes  over  9  pounds  in  the  grain 
alone;  while  a  fifty-bushel  crop  of  wheat,  instead  of  removing  less 
than  one-tenth  of  a  pound,  actually  removes  5.1  pounds.  With  some 
plants,  such  as  alfalfa,  the  sulfur  requirements  were  found  to  be 
actually  greater  than  the  phosphorus  requirements. 


SULFUR  CONTENT  OF  THE  SOIL 

The  results  reported  above  directed  attention  to  the  sulfur  content 
of  the  soil,  and  a  number  of  soils  were  analyzed  for  sulfur,  especially 
by  investigators  in  Wisconsin,  Iowa,  and  Kentucky.  The  amount  of 
sulfur  present  in  the  soil  was  found  to  be  uniformly  low,  and  in  most 
cases  less  than  the  amount  of  phosphorus.  The  results  obtained  at 
•the  Kentucky  station  are  typical,  and  are  recorded  below  as  pounds 


1920}  SULFUR  IN  RELATION  TO  SOIL  FERTILITY  101 

in  two  million  pounds  of  soil   (the  weight  of  an  acre  to  a  depth 
of  6%  inches)  : 

Source  of  Soil  Sulfur             Phosphorus 

Wolfe  county 440                      860 

Lincoln  county 480                      300 

Henry  county 280                       740 

Webster  county 360                       840 

Green  county 360                      600 

Groves  county 240  •  860 

Fayette  county 760  3500 

Marion  county 460  1240 

Jefferson  county 380                      840 

Henderson  county 620  1400 

Average 438  1118 

It  is  quite  clear  from  these  results  that  the  sulfur  content  of  the 
soil  is  very  limited.  Undoubtedly  an  analysis  of  the  soils  of  Illinois 
would  show  similar  results  were  it  worth  while  to  spend  the  time 
and  money  to  make  the  analysis. 

Some  evidence  has  also  been  presented  to  show  that  the  sulfur 
content  of  cropped  cultivated  soils  is  less  than  that  of  corresponding 
virgin  soils. 

These  facts  have  led  some  investigators  to  believe  that  sulfur 
bears  the  same  relation  to  soil  fertility  as  phosphorus,  and  that  in 
a  permanent  system  of  soil  fertility  it  is  necessary  to  add  sulfur  in 
some,  form  to  meet  these  requirements.  This  conception  has  been 
endorsed  with  enthusiasm  by  certain  commercial  interests,  and  an 
active  propaganda  is  now  being  carried  on  to  promote  sales  of  sulfur- 
bearing  fertilizers.  That  there  is  no  sufficient  basis,  for  this  belief 
is  fully  borne  out  by  the  following  data. 

EFFECT  OF  SULFUR  ON  THE  PRODUCTION  OF  CROPS 

A  number  of  pot-culture  experiments  to  determine  the  effect  of 
sulfur  fertilization  on  the  production  of  crops  have  been  reported 
by  various  investigators  as  meeting  with  more  or  less  indifferent  suc- 
cess. The  results  obtained  by  Hart  and  Tottingham  are  probably 
typical.  They  found  that  calcium  sulfate,  or  gypsum,  alone  increased 
the  yield  of  clover  23  percent.  When  gypsum  was  added  to  a  com- 
plete fertilizer,  the  yield  of  rape  was  increased  17  percent  and  the 
yield  of  radishes  9  percent.  A  number  of  similar  pot  experiments 
have  been  carried  on  in  the  greenhouse  by  investigators  elsewhere, 
with  very  similar  results.  The  pot  cultures  so  far  reported  are  in- 
validated, however,  as  evidence  on  this  question  because  no  compensa- 
tion was  allowed  for  tlie  sulfur  wliicli  may  Tiave  been  added  to  tlie 
soil  by  rainfall  under  field  conditions. 

During  the  latter  part  of  the  eighteenth  and  the  early  part  of 
the  nineteenth  centuries,  gypsum  was  commonly  used  In  many  sec- 


102  BULLETIN  No.  227  [June, 

tions  of  the  country,  and  articles  were  written  recording  the  benefit 
derived  by  various  farmers  from  its  use.  These  results,  however, 
have  no  scientific  background,  and  hence  have  little  value  as  evidence 
and  must  be  classed  only  as  interesting  historical  observations.  The 
best  and  most  reliable  data  the  world  affords  is  that  furnished  by 
the  Ohio  and  Pennsylvania  experiment  stations,  where  gypsum  has 
been  used  for  many  years  in  the  regular  experimental  work  and 
definite  records  of  yields  and  soil  treatment  are  available. 

The  data  obtained  at  the  Pennsylvania  station  are  wholly  negative ; 
no  benefit  at  all  is  shown  from  the  use  of  gypsum.  Plots  13  and  33 
received  an  application  of  320  pounds  of  land- plaster  (gypsum) 
applied  in  alternate  years.  The  thirty-five-year  average  yields  on 
thece  plots  were  as  follows:  corn,  36.1  bushels;  oats,  31.3  bushels; 
wheat,  13.4  bushels;  hay,  2,378  pounds;  while  the  average  yield  of 
the  untreated  plots  was  corn,  37.2  bushels;  oats,  31.6  bushels;  wheat, 
13.4  bushels;  and  hay,  2,460  pounds.  Ground  limestone  alone  gave 
an  average  yield  of  42  .bushels  of  corn,  34.2  bushels  of  oats,  15.6 
bushels  of  wheat,  and  2,760  pounds  of  hay. 

Altho  the  results  obtained  at  the  Ohio  experiment  station  in  ex- 
periments with  acid  phosphate,  raw  rock  phosphate,  and  gypsum 
when  used  to  reenforce  farm  manure,  appear  to  be  very  favorable  to 
the  use  of  gypsum  under  certain  conditions,  it  should  be  realized 
fully  that  there  are  several  ways  of  interpreting  the  data  presented 
by  that  station.  It  seems  to  the  writer  that  the  logical  way  to  deter- 
mine the  effect  of  farm  manure  is  to  compare  the  average  yield  of 
the  plots  receiving  manure  alone  with  the  average  yield  of  all  check 
plots  in  the  series.  The  effect  of  acid  phosphate,  raw  rock,  or  gypsum 
may  likewise  be  ascertained  by  comparing  the  yield  obtained  by 
manure  reenforced  with  any  one  of  these  materials,  with  the  yield 
obtained  by  manure  alone. 

The  eighteen-year  average  yield  of  crops  obtained  at  Ohio  with 
the  various  treatments  are  recorded  below: 

Corn,  Wheat,  Hay, 

bu.  bu.  Ibs. 

Unmanured 31.77  11.76  2,536 

Manure,  untreated 56.11  21 . 37  3,668 

Manure,  rock  phosr)hat3 65.07  25.70  4,561 

Manure,  acid  phosphate 65 . 36  26 . 81  4,555 

Manure,  gypsum 61.05  24.30  3,897 

The  increases  due  to  the  treatments  were  therefore  as  follows : 

Corn,  Wheat,  Hay, 

bu.  bu.  Ibx. 

Manure,  alone 21.34  9.61  1,132 

Raw  rock  phosphate 8 . 96  4 . 33  893 

Acid  phosphate 9.25  5.44  887 

Gypsum 4.94  2.93  229 


1920]  SULFUR  IN  RELATION  TO  SOIL  FERTILITY  103 

There  are  very  striking  results.  The  soil  is  very  deficient  in  nitro- 
gen and  phosphorus,  and  responds  markedly  to  those  substances  when 
they  are  applied  in  the  form  of  organic  manures  or  inorganic  phos- 
phates. Manure,  applied  at  the  rate  of  8  tons  per  acre  every  three 
years,  has  produced  a  markedly  increased  yield.  This  amount  of 
manure,  however,  has  not  been  sufficient  to  meet  the  requirements 
of  the  plant  for  food,  as  is  evidenced  by  the  fact  that  phosphorus, 
either  as  acid  phosphate  or  raw  rock,  when  added  to  the  manure  has 
produced  still  larger  yields. 

The  raw  rock  phosphate,  acid  phosphate,  and  gypsum  were  applied 
at  the  rate  of  320  pounds  per  acre  every  three  years.  Gypsum  alone 
has  produced  an  increase  of  4.9  bushels  of  corn,  2.9  bushels  of  wheat, 
and  229  pounds  of  hay.  Acid  phosphate,  which  consists  of  both 
soluble  monocalcium  phosphate  and  gypsum,  has  produced  an  increase 
of  9.3  bushels  of  corn,  5.4  bushels  of  wheat,  and  887  pounds  of  hay; 
while  rock  phosphate,  containing  twice  as  much  phosphorus  but  no 
gypsum,  has  produced  an  increase  of  9  bushels  of  corn,  4.3  bushels 
of  wheat,  and  893  pounds  of  hay.  In  other  words,  when  manure 
has  been  reeiiforced  v/ith  the  larger  amount  of  phosphorus  contained 
in  the  raw  rock,  yields  have  been  produced  practically  equal  to  those 
produced  by  the  combined  action  of  monocalcium  phosphate  and  gyp- 
sum in  the  acid  phosphate. 

These  experimental  results  obtained  at  Ohio  are  not  only  the  best 
the  world  affords  concerning  the  use  of  gypsum  but  they  are  in  com- 
plete harmony  with  what  one  would  expect  as  a  result  of  the  well- 
known  stimulating  action  of  gypsum.  When  sufficient  phosphorus 
has  not  been  applied,  either  in  the  farm  manure  or  in  the  applied 
phosphate,  then  the  application  of  gypsum  has  enabled  the  plant  to 
better  draw  on  the  inadequate  supply  of  phosphorus  already  in  the 
soil,  owing  to  the  stimulation  of  bacterial  life,  as  shown  by  Greaves, 
and  the  more  abundant  development  of  root  hairs  (a  well-known  effect 
of  calcium  compounds),  as  recently  shown  anew  by  Hart  and  Totting- 
ham.  When  sufficient  phosphorus  has  been  applied  in  the  form  of 
raw  rock,  however,  the  needs  of  the  plant  have  been  met  without 
the  aid  of  the  stimulating  action  of  gypsum.  It  is  quite  evident  that 
the  apparently  beneficial  action  of  gypsum  is  due  to  the  stimulating 
effect  described  and  not  to  the  addition  of  calcium  or  sulfur  as 
plant  foods. 

An  abundance  of  data  is  also  available  from  the  investigations  of 
the  Illinois  Experiment  Station  regarding  the  effect  of  applications 
of  sulfur,  on  the  production  of  common  farm  crops.  Potassium 
sulfate  is  regularly  used  in  the  experimental  \vork.  The  yield  of 
crops  from  some  of  the  Davenport  plots  of  the  Urbana  North  Farm 
arc  recorded  in  Table  2. 


104 


BULLETIN  No.  227 


[June, 


TARLE  2. — EFFECT  OF  SULFUR  ON  THE  YIELD  OF  CROPS  ON  BROWN  SILT  LOAM  : 
ILLINOIS  EXPERIMENTS  (Yields  expressed  in  bushels  or  (tons)  per  acre) 


Treatment 

Corn 
19  crops 

Oats 

17  crops 

Wheat 
7  crops 

Clover 
8  crops 

Soybeans 
4  crops 

Alfalfa 
6  crops 

Grain  System  of  Farming 

I?LP         

75  4 

64.2 
64.4 

42.5 

41.7 

2.16 
'  1.64 

22.6 
24.2 

(3.56s) 
(3.50) 

RLPS  

75.6 

Live-Stock  System  of  Farming 

MLP  

72.6 
71.6 

63.5 
62.9 

40.1 
39.4 

(3.62) 
(3.57) 

(1.92) 
(2.09) 

(3.55) 
(3.63) 

MLPS  

ll=rcsidues ;  M=manure;  L=limestone;  P— phosphorus ;   S— sulfur. 

These  results,  extending  over  a  period  of  years,  clearly  demonstrate 
that  sulfur  is  not  a  factor,  on  brown  silt  loam  soil  at  least,  in  the  pro- 
duction of  such  common  farm  crops  as  corn,  oats,  wheat,  clover,  and 
alfalfa  hay,  under  Illinois  conditions. 


LOSS  OF  SULFUR  IN  DRAINAGE  WATER 

Sulfur  occurs  in  the  soil  cither  in  a  form  soluble  in  water,  or  in 
organic  combination  which  is  converted  slowly  into  the  soluble  form, 
and  hence  may  be  readily  lost  from  the  soil  in  the  drainage  water. 
The  amount  so  lost  annually  is  variable.  As  estimated  from  the 
Rothamstcd  data,  the  loss  varies  from  20  to  80  pounds  per  acre, 
depending  upon  the  treatment  which  the  soil  has  received.  Norton, 
from  the  data  obtained  by  measurement  of  the  flow  of  Richland 
Creek,  Arkansas,  and  from  the  composition  of  the  water,  has  estimated 
the  annual  loss  at  6  pounds  per  acre.  The  estimates  of  a  number  of 
European  investigators  vary  from  8  pounds  to  as  high  as  270  pounds 
per  acre  per  annum,  depending  again  upon  the  treatment  of  the 
soil  and  the  conditions  of  the  experiments. 

The  most  satisfactory  data  on  this  question  are  those  obtained 
in  the  lysimeter  experiments  by  the  Cornell  experiment  station  and 
recently  reported  by  Lyon  and  Bizzell ;  part  of  the  results  (expressed 
in  pounds  per  acre)  are  recorded  below: 


Tank 
No. 

3 
5 


Treatment 

Manure,  rotation  of  crops 

Manure,  rotation  of  crops  includ- 
ing clover 


Sulfur  in 

drainage 

water 

31.8 

31.5 


Added  in 
manure 

15.5 
15.5 


Net  annual 

loss  from 

soil 

16.3 

16.0 


Lime,  manure,  rotation  of  crops. . 
Lime,  manure,  rotation  of  crops 
including  clover 


43.9  15.5  28.4 

41.0  15.5  25.5 

Farm  manure  at  the  rate  of. twenty  tons  per  acre  was  applied 

to  these  tanks.     The  amount  of  sulfur  applied  in  the  manure  was 


1920}  SULFUB  IN  RELATION  TO  SOIL  FERTILITY  105 

estimated  to  be  G2  pounds  per  acre,  which  is  equivalent  to  an  annual 
application  of  151/2  pounds.1  Other  data  show  quite  clearly  that 
the  loss  of  sulfur  in  the  drainage  is  dependent  on  the  soil  treatment 
and  particularly  on  the  amount  of  sulfur  applied  in  the  fertilizer. 
Caustic  lime,  as  shown  by  the  data  here  presented,  has  a  marked 
effect  on  loss  of  sulfur  in  the  drainage  water.  Allowing  for  the 
sulfur  added  in  the  manure,  the  net  annual -loss  of  sulfur,  where  a 
rotation  of  crops  was  practiced  and  manure  used,  varied  from  16  to 
28.4  pounds  per  year.  This  loss  occurred  after  the  requirements  of 
the  plants  had  been  completely  met  and  must  therefore  represent 
an  annual  excess  of  unusable  material.  In-  a  permanent  system  of 
soil  fertility,  must  this  loss  be  met  each  year  by  the  addition  of 
some  form  of  sulfur  materials  ?  Why  add  more  soluble  sulfur,  which 
only  increases  the  amount  lost  in  the  drainage,  since  there  is  already 
an  excess  of  available  sulfur  in  the  soil  which  the  plant  refuses  to 
utilize?  These  two  questions  are  perfectly  justified  at  this  point  and 
warrant  careful  and  serious  consideration. 

Nitrogen,  likewise,  is  lost  in  appreciable  quantities  from  the  soil 
in  the  drainage  water,  especially  from  bare  soil  or  a  soil  growing 
a  cultivated  crop  only  part  of  the  time.  But  nitrogen  is  used  by 
the  growing  plant,  and  when  the  soil  is  kept  in  a  continuous  crop 
the  loss  in  the  drainage  water  may  be  largely,  if  not  entirely,  pre- 
vented. This  is  clearly  shown  by  the  work  of  Babcock  at  the  Geneva 
experiment  station,  who  "studied  the  loss  of  nitrogen  in  the  drainage 
water  from  three  tanks — one  bare  but  undisturbed,  one  cultivated, 
and  one  in  a  continuous  grass.  He  obtained  the  following  results, 
expressed  in  pounds  per  acre: 

Lysimeter  No 1  2  3 

Treatment In  sod  Bare,  Cultivated, 

undisturbed  not  cropped 

Loss  of  nitrogen 1884 .19  69.5  132.0 

1885 1.02  218.7  218.0 

1886 .08  357.7  234.0 

The  nitrogen,  so  essential  as  a  plant  food,  was  practically  entirely 
removed  from  the  drainage  water,  owing  to  the  demands  of  the  plant. 
Therefore,  in  a  native  condition,  the  loss  of  nitrogen  from  the  soil 
is  reduced  materially,  since  a  crop  is  constantly  present,  and  such 
loss  as  does  take  place  usually  more  than  compensated  for  by  the  fixa- 
tion of  atmospheric  nitrogen  by  various  agencies. 

The  work  of  Lyon  and  Bizzel  at  Cornell,  on  the  other  hand,  shows 
quite  conclusively  that  the  loss  of  sulfur  in  the  drainage  water  is 
not  so  reduced  by  cropping,  and  hence  the  sulfur  in  the  drainage 


phosphorus  is  required  by  the  growing  animal  for  bone  production 
and  is  absorbed  from  the  feed  it  consumes,  sulfur  is  not  so  required.  Sulfur 
occurs  in  large  amounts  in  hay,  straw,  stover,  etc.,  and  consequently  finds  its 
•way  into  the  manure.  Farm  manure,  therefore,  contains  slightly  more  sulfur  than 
phosphorus. 


106 


BULLETIN  No.  227 


[June, 


water  must  represent  an.  excess  of  unusable  material.  Their  results 
show  clearly  that  the  loss  of  sulfur  in  the  drainage  water  is  five  or 
six  times  as  great  as  is  the  amount  removed  by  the  crop.  Moreover, 
if  sulfur  is  lost  from  the  soil  in  such  large  quantities  as  some  in- 
vestigators believe,  and  there  is  no  compensation  as  in  the  case  of 
nitrogen,  cultivated  soil  should  very  soon  be  actually  devoid  of  sulfur. 
The  soils  of  Kentucky,  for  example,  having  an  average  sulfur  con- 
tent of  438  pounds  should  be  completely  deprived  of  sulfur  in  ten 
or  fifteen  years  unless  sulfur  is  constantly  being  added  in  appreciable 
quantities  from  some  natural  source. 

SULFUR  CONTENT  OF  RAINFALL 

The  atmosphere  contains  a  variable  quantity  of  sulfur  as  sulfur 
dioxid.  The  quantity  is  quite  appreciable  near  smelters  or  near  large 
cities,  and  cases  have  frequently  been  reported  of  damage  being  done 
to  vegetation  and  household  fabrics  by  the  production  of  sulfuric  acid 
by  the  oxidation  of  the  sulfur  dioxid  of  the  air.  Undoubtedly  the 
amount  of  sulfur  dioxid  in  the  atmosphere  is  less  in  the  open  country 
than  near  large  cities,  but  wherever  coal  or  wood  is  burned  or  organic 
matter  decomposes,  the  sulfur  in  a  large  measure  escapes  into  the 
air  and  the  supply  of  sulfur  in  the  air  is  thus  constantly  being 
replenished. 

The  sulfur  dioxid  of  the  air  is  absorbed  by  the  moisture  in  the 
air  and  added  to  the  soil  in  the  rainfall  (some  is  also  added  to  the 
soil  by  direct  absorption  from  the  air).  The  amount  of  sulfur  so 
added  has  been  found  to  be  very  appreciable  and  to  fully  compensate 
for  that  removed  by  crops  and  lost  in  the  drainage  waters.  Some  very 
significant  data  on  this  phase  of  the  question  have  been  obtained  at 
the  University  of  Illinois  during  the  past  seven  years  and  are  re- 
ported in  Tables  3  and  4. 

TABLE  3. — SDLFUR  ADDED  TO  THE  SOIL  BY  RAINFALL:    ILLINOIS  EXPERIMENTS 
(Amounts  expressed  in  pounds  per  acre) 


Month 

1913 

1914 

1915 

1916 

1917 

1918 

1919 

Aver. 

Jan  

4.3 

2.9 

5.8 

7.5 

3.7 

3.5 

4.2 

4  6 

Feb  

2.7 

6.9 

3.4 

2.7 

3.3 

6  0 

5.1 

4  3 

Mar  

4.5 

4.0 

4.0 

4.7 

5  1 

3.7 

(!) 

4  3 

Apr  

4.1 

4.2 

3.0 

4.6 

5.0 

6.0 

3.2 

4.3 

May  

1.6 

2.2 

5.1 

8.6 

5.6 

4.8 

5.8 

4.8 

June  

2.6 

2.7 

3.3 

5.2 

4.6 

4.3 

4.5 

3.9 

July.. 

2.0 

2.0 

4.4 

1.9 

3.1 

2.2 

1.8 

2.5 

Aug.  .  . 

2.0 

5.7 

4.1 

2.0 

4.3 

4.7 

4.7 

3.9 

Sept  

3.3 

3.0 

3.0 

2.3 

2  5 

3.4 

3.0 

2.9 

Oct  

5.1 

3.0 

1.6 

5.0 

4.9 

5  8 

2  9 

4.0 

Nov  

4.4 

2.4 

2.5 

3  1 

3  9 

2.4 

3  0 

3.1 

Dec  

3.4 

1.6 

5  4 

3.3 

1  7 

.7 

1  6 

2.5 

Total  

40  0 

40  5 

45  5 

51  0 

47  7 

47  6 

39  8' 

45  1 

Aver  

3.3 

3.4 

3.8 

4.3 

4.0 

4.0 

3.6 

3.8 

record  of  March  rainfall 


19X01 


107 


In  1912  a  rain  gage  was  established  on  the  roof  of  the  Agricultural 
Building;  the  rain  water  was  collected  and  measured,  and  monthly 
samples  were  analyzed  for  various  forms  of  nitrogen  and  sulfur. 
The  results  shown  in  Table  3  were  obtained. 

It  may  be  noted  that  from  40  to  51  pounds  of  sulfur  was  brought 
down  annually  in  the  rain  water.  The  amount  added  to  the  soil 
monthly  varies  from  year  to  year.  As  an  average  of  the  seven  years' 
work,  45.1  pounds  of  sulfur  has  been  added  annually,  or  3.8  pounds 
monthly.  This  is  a  large  amount  as  compared  with  the  requirement 
of  crops,  as  shown  on  page  100.  (In  considering  the  variation  from 
month  to  month  it  should  be  borne  in  mind  that  the  amount  of  sulfur 
collected  depends  directly  upon  the  amount  of  precipitation  and  will 
vary  accordingly.)  During  the  period  of  five  months  from  May  to 
September,  18.0  pounds  was  added. 

In  1915  the  Hopkins  soil  bins  were  constructed  in  order  to  study 
certain  special  problems  in  soil  fertility.  These  bins  are  located  on 
the  University  North  Farm  at  Urbana,  under  actual  field  conditions. 
A  rain  gage  was  established  in  connection  with  the  bins  and  the 
rainfall  collected,  measured,  and  analyzed.  The  three  years'  results 
available  from  this  rain  gage  are  presented  in  Table  4. 

TABLE  4. — SULFUR  ADDED  TO  SOIL  BY  RAINFALL:    ILLINOIS  EXPERIMENTS 
(Amounts  expressed  in  pounds  per  acre) 


Month 

1917 

1918 

1919 

Aver. 

Jan  

1  0 

2  3 

4.1 

2  5 

Feb  

6 

4  2 

5.9 

3  6 

Mar  

2  9 

3  9 

5  4 

4  1 

Apr  

3.3 

7.5 

2.9 

4.6 

May  

4.6 

4.7 

4.6 

4.6 

June  

3  2 

3  6 

3  7 

3  5 

July.. 

2.5 

2.0 

2.8 

2.4 

Aug.  .  . 

3.7 

2.8 

2.2 

2  9 

Sept  

2.6 

4.5 

1.8 

3.0 

Oct  

3.9 

4.8 

3.8 

4.2 

Nov  

2.8 

3.4 

2.9 

3.0 

Dec  

.5 

5.8 

.9 

2.4 

Total  

31  5 

49  4 

41  0 

40  8 

Aver  

2.6 

4.1 

3.4 

3.4 

Again  there  is  a  variation  from  month  to  month  in  the  amount 
of  sulfur  added  to  the  soil  in  the  rainfall.  As  an  average  of  the 
three  years  covered  by  these  data,  40.8  pounds  was  found  to  have 
been  added  annually,  or  3.4  pounds  monthly.  During  the  growing 
period  for  corn  (from  May  to  September)  16.4  pounds  was  added 
to  the  soil. 

From  the  data  presented,  it  is  quite  evident  that  the  sulfur  supply 
of  the  soil  is  automatically  replenished  from  the  atmosphere  and 
that  the  relation  of  sulfur  to  soil  fertility  is  not  in  any  sense  similar 


108  BULLETIN  No.  227  [June, 

to  that  of  phosphorus.  For  example,  to  produce  a  hundred-bushel 
crop  of  corn  17  pounds  of  phosphorus  and  9  pounds  of  sulfur  are 
required  for  the  grain  alone.  The  phosphorus  must  come  either  from 
the  soil  or  from  applied  materials,  for  there  is  no  other  possible  source. 
On  the  other  hand,  the  results  obtained  at  the  Hopkins'  soil  bins 
indicate  that  under  actual  field  conditions  an  average  of  16.4  pounds 
of  sulfur  is  added  to  the  soil  during  the  growing  season  for  corn 
(from  May  to  September),  and  that  this  sulfur  is  added  in  monthly 
installments  of  3.4  pounds.  Very  fortunate  would  we  be  could  our 
phosphorus  and  limestone  problems  be  so  easily  solved! 


CONCLUSIONS 

The  only  conclusion  that  can  be  drawn  from  the  available  data 
on  this  subject  is  that,  under  humid  conditions,  sulfur  need  not  be 
added  to  the  soil  as  a  plant  food.  This  does  not  in  any  sense  detract 
from  the  possibility  of  its  use  in  other  ways.  It  may,  for  example, 
have  a  very  important  use  as  a  germicide  or  as  a  fungicide  in  plant 
production  problem.  Mixed  with  rock  phosphate  in  the  compost  heap, 
as  advocated  by  Lipman,  it  may  have  some  value  as  a  market-garden 
proposition,  but  this  is  simply  a  method  for  producing  acid  phosphate 
on  the  farm  and  should  not  be  confused  at  all  with  the  use  of  sulfur  as 
a  plant  food.  Likewise,  the  question  of  making  available  the  phos- 
phorus in  raw  rock  in  the  soil  by  using  it  in  connection  with  gypsum, 
may  have  some  merit  owing  to  the  stimulating  action  of  gypsum  on 
the  bacterial  activity  in  the  soil  and  the  increased  root  production  of 
the  plant;  but  this  again  is  an  entirely  separate  problem  from  the 
use  of  gypsum  as  a  source  of  the  plant  food,  sulfur. 

We  must  conclude  that  the  sulfur  problem,  in  relation  to  soil  fer- 
tility, is  not  in  any  sense  similar  to  the  phosphorus  problem.  It  has 
rather  a  relation  similar  to  carbon,  for  both  sulfur  and  carbon  are 
supplied  to  the  plant  from  the  atmosphere,  in  amounts  sufficient  for 
its  requirements,  and  this  supply  is  constantly  being  replenished  by 
natural  processes. 


UNIVERSITY  OF  ILLINOIS-URBANA 


